1. Field of the Invention
The present invention relates to a self-healing network for ensuring continued communication service in the event of a link failure using alternate routes. The present invention is particularly suitable for ATM (asynchronous transfer mode) self-healing networks.
2. Description of the Related Art
In the event of a link failure in an ATM communication network, an alternate virtual path is selected so that its bandwidth guarantees the bandwidth used by the failed virtual path. A known fault recovery scheme involves the provisioning of pre-arranged alternate paths of same bandwidths as working paths and performing instant switching to the pre-arranged paths when the working paths fail. While the outage time can be reduced to a minimum, the disadvantage is that a significant amount of network resources is required.
According to another well known method, path-finding messages are broadcast through the network for making a search through all possible paths which may exist between failure-affected nodes for an alternate path having the same bandwidth as the failed path. If a path of the same bandwidth is detected, the affected path is switched to the detected path. Since the path-finding messages are affected by the amount of traffic carried through the network, it is difficult to guarantee the recovery of the same bandwidth and hence the continuity of service.
Another technique, as disclosed in Japanese Laid-Open Patent Specification Hei 7-235923, involves the provisioning of pre-established "connections" of zero bandwidth corresponding to working paths. When a link failure occurs in a working path, an alternate path is formed by allocating the same bandwidth to the corresponding pre-established connection. However, this technique suffers from the same problem as the path-finding technique because of the difficulty in guaranteeing the required bandwidth for the pre-established connection.